Fossil fuel burners convert chemical energy stored in fossil fuels to thermal heating by combusting the fossil fuel in the presence of an oxidant. In power generating applications, thermal heat may be transferred to water in order to produce steam for driving electricity producing turbines. In non power generating applications, thermal heat can be transferred to any number of conceivable objects or processes.
Conventional steam generating boilers generally comprise of one or more burners, one or more fuel injection points, one or more oxidant injection points, and a means for propelling the injected fuel and oxidant into a combustion furnace. Upon ignition of the oxidant/fuel mixture (FIG. 1) a combustion envelope 4 is formed comprising a flame 3 and an oxidant/fuel mixing zone 2 between the flame 3 and the burner 1.
FIGS. 2 and 3 are schematic representations of conventional steam generating boilers utilizing a single and multiple burner(s) respectively. The interior walls comprise a plurality of steam generating tubes 6 fluidly connected to a boiler bank (not shown). Thermal energy produced within the combustion envelope 4 radiantly heats the tubes 6 which in turn conduct thermal energy to the water in the tubes 6 for the purpose of generating steam.
In many steam generating boilers, the length and width of the combustion envelope 4 play an integral role in the design of the combustion furnace 5. In FM boilers, for example, the combustion furnace 5 is preferably designed sufficiently large enough to avoid excessive contact of the combustion envelope 4 with the furnace walls 10. Also known as flame impingement, seen in FIG. 3, excessive flame 3 contact with a furnace wall 10 may result in incomplete combustion, leading to higher emissions of CO and other combustion byproducts, or premature degradation, leading to costly repairs and boiler downtime. Accordingly, combustion furnaces 5 are generally designed to accommodate a given burner combustion envelope 4 while minimizing the possibility of flame impingement.
Conventional burners generally utilize flow control mechanisms to control the axial and radial expansion of the combustion envelope 4. Radial expansion of the combustion envelope 4 is generally a function of swirl and the natural expansion of the fuel, oxidant, and flame. Some conventional burner designs utilize flow control mechanisms to restrict the natural radial expansion of the combustion envelope 4, resulting in a longer narrower flame. Shearing forces created by flow control mechanisms may also be used to influence the extent of oxidant/fuel mixing prior to combustion, thereby having an effect on emissions such as CO and NOx.
The availability of oxidant and fuel and their ability to mix prior to combustion influences the length of a combustion envelope 4 within a combustion furnace 5. Longer flames generally result from an insufficient supply of oxidant or inadequate mixing of the oxidant and fuel within the combustion envelope 4. Shorter flames generally result from a sufficient supply of oxidant and adequate mixing of the oxidant and fuel within the combustion envelope 4. Flame length may also be influenced by the velocity at which fuel and/or oxidant streams enter the combustion envelope 4. Excessive velocities or momentary interruptions of fuel and/or oxidant streams may cause the burner flame 3 to lose ignition. Such loss of ignition is especially undesirable, as it may result in an accumulation of combustibles susceptible to violent explosion upon reignition.
The U.S Department of Energy has articulated that a long felt need exists to reduce the size and weight of steam generator boilers such as industrial boilers. Conventional steam generating boilers are built to accommodate the size of the combustion envelope 4 produced. Accordingly, a long felt need exists to develop a combustion envelope 4 capable of producing sufficient thermal energy for steam production in a significantly smaller volume, thereby allowing the production of smaller, lighter, and more compact steam generating boiler designs.